Auto-sync with upstream branch master
    
    Upstream commit c1c0dea38833751f36a145c322ce53c9a08332e1
    
    - Linux: Remove epoll_create, inotify_init from syscalls.list (#2154747)
    - Linux: Reflow and sort some Makefile variables
    - mach: Drop remnants of old_CFLAGS
    - mach: Fix passing -ffreestanding when checking for gnumach headers
    - Force use of -ffreestanding when checking for gnumach headers
    - elf: Fix tst-relro-symbols.py argument passing
    - x86: Prevent SIGSEGV in memcmp-sse2 when data is concurrently modified [BZ #29863]
    - Allow _Qp_fgt in sparc64 localplt.data